This application claims the priority of 198 32 875.3-21, filed Jul. 22, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for controlling the brake system of a vehicle having a controllable service brake and a controllable retarder controlled in a mutually coordinated manner.
A known control method is disclosed, for example, in DE 196 04 391 A1. The fractions of the service brake and of the retarder are coordinated with one another so that, during adjustment of the service brake, the actual braking performance of the retarder is taken into account. In addition, operating parameters of the vehicle in the form of axle load signals, vehicle speed and the like are taken into account when determining the retarder and service brake fractions.
An object of the present invention is to further improve a vehicle brake system control method such that lower stress to components and longer brake lining service lives of the service brake are achieved while optimizing the braking effect of the vehicle.
In such a method for controlling the brake system of a vehicle, this has been achieved according to the invention by activating the retarder during each braking operation and automatically controlling the retarder as a function of the driver""s braking desire, driving condition quantities, and/or road condition quantities of the vehicle (integrated operation of the retarder).
This integrated retarder operation achieves a reduction of the braking fraction of the service brake and leads to a lower stress to components and to longer brake lining service lives. Simultaneously control of the retarder as a function of driving condition values, road condition values and/or operating conditions of the vehicle achieves an optimal coordination of the braking effect of the service brake and the retarder with respect to one another. In particular, by the detection of the road condition values during braked and unbraked driving, adhesion conditions are also detected and taken into account when the retarder is operated and during the simultaneous operation of the service brake.
Advantageously, the service brake is activated first and then the retarder is activated. This particularly results in a fast response of the brake during a braking operation. In the case of very critical road conditions, a high adhesion requirement of the service brake alone already exists at an early stage so that retarder fractions are no longer permitted at all.
Furthermore, one advantageous currently contemplated embodiment provides that the retarder and the service brake are controlled such that the braking effect generated by the service brake does not fall below a defined fraction of the total braking effect during each braking operation. In a particularly advantageous manner, this prevents a glazing of the brake linings. This minimum fraction permits a spontaneous readjustment of fluctuating retarder effects, for example, during transmission shifting operations. Thereby, the driver""s deceleration desire is always observed.
Furthermore, the retarder is preferably operated externally. The external operation by the driver always has priority over fractions of the integrated operation. The external operation is therefore generally considered as an additional braking desire.
It is particularly advantageous that the adhesion conditions are detected and the retarder fraction is coordinated with these conditions by the determination of the slip requirement of the retarder. As the result of this adhesion monitoring, the braking effect of the retarder as well as of the service brake is adapted to the road condition. Furthermore, the retarder fraction is advantageously adapted to the load condition of the vehicle.
In the method according to the present invention, advantageously no mechanical switch-off possibility of the integrated retarder is required. This also eliminates particularly switches, circuits and the like for switching off the retarder, and is particularly advantageous with respect to the manufacturing and particularly also with respect to the manufacturing costs.